Bjorkman, Anne , Vellend, Mark .
Changes in vegetation patterns on Vancouver Island and Saltspring Island (British Columbia, Canada) since European settlement.
Early land survey records can be used to reconstruct the historical distribution and abundance of tree species prior to the large-scale impact of industrialized societies. Comparing these records to current vegetation patterns allows us to examine the shifts that have occurred in plant communities since the arrival of European settlers in North America. We used presettlement (1859-1874) land survey records from southeastern Vancouver Island and Saltspring Island, British Columbia, Canada to reconstruct the relative abundance and density of tree species in these areas. We then collected equivalent vegetation data from the same points in the modern landscape, which enabled us to compare the two points in time and identify the changes in large-scale vegetation patterns that have occurred since European settlement. Our results show a significant increase in the relative abundance of maple (Acer macrophyllum) and cedar (Thuja plicata), and a corresponding decrease in Douglas-fir (Pseudotsuga menziesii). Furthermore, there has been a considerable increase in tree density in undeveloped areas. The 1859 records indicate that 43% of the land surveyed was made up of prairies or open “plains” (with average stem densities of 10 and 34 stems per hectare, respectively) while forests (270 stems/ha) made up only 27%. Based on comparable density measures from 2007, prairies and plains now represent less than 5% of the undeveloped landscape, while forests comprise nearly 90%. These changes are likely due to a combination of factors that have been influenced by European settlement. In particular, suppression of fire has likely led to an infilling of trees into previously open areas and also may have caused the observed increase in abundance of fire-sensitive species such as cedar.
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1 - University of British Columbia, Botany, 3529-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
2 - University of British Columbia, Botany and Zoology, 3529-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 10:45 AM